The main objective of this program is to expand our knowledge of the pathogenesis and treatment of schistosomiasis, leprosy and leishmaniasis. The Tropical Medicine Research Center will increase our collaboration with American scientists and provide opportunities for United States investigators to conduct research on tropical diseases. Major diseases which are endemic in the State of Bahia, brazil include: leishmaniasis, schistosomiasis, filariasis, Chagas' disease, leprosy, malaria and strongyloidiasis. The overall goals are to increase our understanding of host defense mechanisms against S. mansoni and leishmania and to improve methods for the treatment of leishmaniasis and leprosy. Project 1, Host Immune Response in Schistosomiasis will identify factors contributing to host resistance to reinfection. The specific aim is to correlate cellular immune responses with susceptibility to S. mansoni infection and to identify antigens that are involved in immuno protection. Project 2, T Cell responses in Human Leishmaniasis will examine T cell responses and the role of cytotoxic cells in the control of leishmania infection and histological aspects of cutaneous, mucosal and visceral leishmania infection and histological aspects of cutaneous, mucosal and visceral leishmaniasis. Project 3, Immunotherapy of Leprosy and Leishmaniasis will evaluate therapy with gamma interferon in combination with conventional therapy in patients with diffuse and cutaneous leishmaniasis and leprosy. Patients with leishmaniasis and schistosomiasis will be recruited from endemic areas located within the State of Bahia, Brazil.